We need an PAI to get the location  (java.io.File)
of the web app.
There are 2 usage for that:

1/ a server plugin could derive automatically a
contextroot value from the direName of the webapp.
This would minimize the user 'configuratio'
activity a loot

2/ We also need this name to be used byt the first
initial dir deployment to calculate a good ModuleID.

We could use there the context root, but if the
user changes the contextroot, we don't want to do
a full dpeloy again in a different directory.
USing the webapp dir locaiton as the name for the
moudle ID, we cna better handle this moduleID stuff.

3/ It was possible with the previous APIs, so it
could be a regression.
4/This could also be used by the plugin to choice
the lcoation of the deployment plan within the
module source area.